WHAT IS AN EMG?

An EMG test (also known as an electromyogram or electromyography) is a medical examination performed by specially trained physicians to evaluate the function and health of nerves and muscles. Testing usually includes both EMG and nerve conduction studies. This form of testing is considered a separate subspecialty of medicine termed electrodiagnostic medicine or peripheral clinical neurophysiology and has its own board certification process and special training requirements for certification of physicians and technicians performing these studies.

Nerve conduction studies are used to test individual nerves. Peripheral nerves are organs that serve as the "wiring" carrying signals for sensation, muscle commands, and other special functions to and from the brain and spinal cord. The nerves tested travel in predictable routes through the body, well known to each examiner. Testing involves stimulating a nerve with brief, small electrical impulse to the skin surface and recording the response from a muscle or another portion of the nerve via small detection pads on the skin. The electrical stimulations range from barely perceptible to a shock comparable to a static electric shock in winter. These studies are very safe and even the maximal machine output is too small to cause injury. Most studies require only a small fraction of the maximal level. There are no lasting effects. Information on the health of each nerve including the location and type of specific nerve injury is gathered and interpreted.

EMG or electromyography is another type of testing providing complimentary information, usually following nerve conduction studies. In this test a sterile, disposable, very thin needle electrode (about the width of a straight pin (26 gauge)), Teflon coated to ease insertion is placed through the skin into a muscle. The needle is a specialized recording device with a fine internal platinum wire, analogous to an antenna that directly records the muscle's natural electrical activity at rest and during muscle contraction. Analysis of this activity gives important information about the health of each muscle tested as well as the controlling nerves. Each examination is specially tailored to provide information about the specific clinical questions for a given patient.